US pilots previously told not to fly over Ukraine

The Federal Aviation Administration had warned U.S. pilots earlier this year not to fly over portions of Ukraine in the Crimea region, according to notices posted on the agency's website.

The notices were posted on April 23. The U.N.'s International Civil Aviation Organization and the aviation authorities in most countries issue similar notices for areas where unrest or military conflict creates a risk of being shot down.

The FAA had not issued any new warnings Thursday in the immediate aftermath of reports that a Malaysian airliner had been shot down over Ukraine